1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to a multi-party conferencing method in third generation (3G) packet-switched radio telecommunications networks.
2. Description of Related Art
In packet-switched radio telecommunications networks today that utilize the International Telecommunications Union (ITU) H.323 signaling protocol or the Internet Engineering Task Force (IETF) Session Initiation Protocol (SIP), a party cannot originate a multi-party conference call while engaged in an ongoing two-party call. Internet Protocol (IP) call-control protocols such as H.323 and/or SIP include an implicit assumption: the caller knows before establishing the call that he would like this call to be a multi-party call. By indicating during the initial call setup that the call is a multi-party call, the caller informs the entity receiving the call request (the H.323 gatekeeper or SIP server) to engage a Multipoint Control Unit (MCU) in the call from the beginning. The MCU includes a Multipoint Controller (MC) which controls the setup of multi-party conference calls, and a Multipoint Processor (MP) which performs the payload mixing and forwarding required for the conference calls. Thereafter, the MC can add additional parties to the call when requested. However, if two subscribers are engaged in a call that was originally set up as a two-party call, and they desire to conference-in a third party, they must hang up and begin the call again as a multi-party conference call.
This limitation on multi-party conference calls in packet-switched networks is not acceptable for mobile subscribers because it is more restrictive than the procedures available to subscribers in older circuit-switched networks. In circuit-switched networks, a third party can be added after the establishment of a two-party call by placing one party on hold, dialing a feature code and a third-party telephone number, and then connecting the third party. It would be desirable for mobile subscribers using 3G packet-switched networks to have the same capabilities as they have today with circuit-switched networks. The present invention provides a multi-party conferencing method in 3G packet-switched radio telecommunications networks that allows a multi-party conference call to be originated during an on-going two-party call.
In one aspect, the present invention is a multi-party conferencing method in a packet-switched radio telecommunications network in which a call-control server such as an H.323 Gatekeeper or SIP server has established an on-going two-party call between a first party and a second party. The call-control server first receives a message from the first party that includes an indication that a multi-party conference call is desired, and includes at least one telephone number of a third party to be joined in the multi-party conference call. The server then engages a Multipoint Control Unit (MCU) to set up the multi-party conference. A Multipoint Controller (MC) within the MCU provides an Internet Protocol (IP) address of an associated Multipoint Processor (MP) to the first, second, and third parties, and negotiates media sessions with each of the first, second, and third parties using H.245 procedures. The MP then receives media payload from each of the first, second, and third parties, mixes the media payload, and forwards the mixed payload from the MP to each of the first, second, and third parties.
In another aspect, the present invention is a system for joining a third party in a multi-party conference call in a packet-switched radio telecommunications network in which a call-control server has established an on-going two-party call between a first party and a second party. The system includes an MCU and a call-control server. The MCU includes an MP and an MC. The MP receives media payload from the first, second, and third parties, mixes the payload, and forwards the mixed payload to the first, second, and third parties. The MC sets up the multi-party conference call. The MC includes a control link to the MP for obtaining an IP address of the MP, and for providing an IP address of each of the first, second, and third parties to the MP. The MC also includes means for negotiating media sessions using H.245 procedures with each of the first, second, and third parties. The call-control server controls calls in the network and includes a signaling mechanism that communicates with the first, second, and third parties. The signaling mechanism receives a message from the first party that includes an indication that a multi-party conference call is desired and a telephone number of the third party. In response, the call-control server engages the MCU. The signaling mechanism also provides the IP address of the MP to the first, second, and third parties so that their media payload can be sent to the MP for mixing and forwarding.
In yet another aspect, the present invention is a combined Gatekeeper/Multipoint Control Unit (GK/MCU) for joining a third party in a multi-party conference call during an on-going two-party call between a first party and a second party. The GK/MCU includes a GK portion, an MC portion, and an MP portion. The GK portion includes a signaling mechanism that communicates with the first, second, and third parties. The signaling mechanism receives a message from the first party that includes an indication that a multi-party conference call is desired and a telephone number of the third party. In response, the GK portion engages the MC portion. The MC portion includes a control link to the MP portion and means for negotiating media sessions with each of the first, second, and third parties. The control link obtains the IP address of the MP portion which is then passed to the first, second, and third parties by the signaling mechanism in the GK portion. The control link also provides the IP address of each of the first, second, and third parties to the MP portion. Following H.245 negotiations by the MC portion, the MP portion receives media payload from the first, second, and third parties, mixes the payload, and forwards the mixed payload to the first, second, and third parties.